A converter is a circuit intended for converting electrical energy. For the intermediate storage of electrical energy, an intermediate circuit is provided which is connected to a direct current and is generally configured with one or more capacitors. For each phase of the alternating voltage, the intermediate circuit can be provided with two series-connected, controllable switches, arranged parallel thereto, to which respectively one free-wheeling diode can be assigned. These switches are controlled in such a way that an alternating voltage can be tapped at the connecting points of the switches.
A converter of this type, for example, can be a rectifier or an AC/DC converter or in general a power converter.
A power converter circuit is known from the document DE 101 03 031 A1 for which each phase is configured with a plurality of series-connected, identical subsystems. Each subsystem is provided with a capacitor having two series-connected, controllable switches, connected parallel thereto, which are respectively provided with a free-wheeling diode. The capacitors for the subsystems of a phase consequently form the intermediate circuit for this phase.
One disadvantage of the known power converter circuit is that the capacitors of the individual subsystems generally do not have the same charging state, so that the voltages present at the intermediate circuits for the phases are also not the same. During the operation, meaning when the switches are activated, this leads to charge reversals which, in turn, result in oscillating currents between the phases.